Devil's Den Then, Later, and Now

When a then and now just isn't enough....here is a then, later, and now, three images of the same three rocks in Devil's Den with Little Round Top in the background.
Alexander Gardner's classic photo on top shows this area of Devil's Den just as the soldiers who fought here saw it just days before. Bottom left is a look at the same spot around 1960 thanks to George W Pyle Jr who took the photo, and finally, on the right as it appeared just a few years ago in my photo.

Thanks, I remember when I was on Little Round Top a few years ago that the guide said then that the park was trying to get the terrain to look like it did during the war, and that it is an ongoing job.

Acid rain from industrialization, as well as it's other subtle effects, have contributed to the advanced weathering of terrain features like the famous rocks at Gettysburg.

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"Advanced weathering?" I don't think so. Acid rain mostly affects calcium based rocks, such as limestone. The rocks of Devil's Den are made up of similar minerals comparable to granite. These minerals are acid-resistant and weathering occurs at extremely slow rates. Therefore, it is unlikely that there would be any visually weathering effects in only 150 years. If you could quote a reference, that would be helpful.